Methods for the concentration and removal of selected ions from a solution that will often contain a variety of ions, both cationic and anionic, across a wide pH range, represents a real need in the modern era of advanced technologies. A significant improvement in the art does exist which provides for the concentration and/or removal of a selected ion from a solution using an organic ligand that is covalently bound, through an organic spacer, to a solid support such as silica gel, glass beads, alumina, titania, zirconia nickel oxide, polyacrylate, or polystyrene. The organic ligand provides for coordinative or chelative ion bonding with significant levels of selectivity. The combination of organic ligand and solid support provides for the incorporation of such a composition into a column for subsequent use much as pure silica gel is used in column chromatography. By passing a solution containing ions, wherein one ion is desired to be trapped to the exclusion of any other ions, through a column containing a suitable ligand designed to trap the targeted ion, the targeted ion is selectively and exclusively removed from the solution. The trapped ion may be flushed or "un-trapped" by passing a second solution through the column. The second solution is formulated such that it has a greater affinity for the trapped ions than the ion trap ligand does, allowing for the trapped ions to be flushed from the column. In this manner the targeted ion is selectively removed from any other ions in the solution.
Compositions comprising selective ion binding organic ligands covalently attached to solid supports through organic spacers, such as described above, are illustrated in numerous patents, of which the following are representative: U.S. Pat. No. 4,952,321 to Bradshaw et al. discloses amine-containing hydrocarbon ligands; U.S. Pat. Nos. 5,071,819 and 5,084,430 to Tarbet et al. disclose sulfur and nitrogen-containing hydrocarbons as ion-binding ligands; U.S. Pat. Nos. 4,959,153 and 5,039,419 to Bradshaw et al. disclose sulfur-containing hydrocarbon ligands; U.S. Pat. Nos. 4,943,375 and 5,179,213 to Bradshaw et al. disclose ion-binding crowns and cryptands as ligands; U.S. Pat. No. 5,182,251 to Bruening et al. discloses aminoalkylphosphonic acid-containing hydrocarbon ligands; U.S. Pat. No. 4,960,882 to Bradshaw discloses proton-ionizable macrocyclic ligands; U.S. Pat. No. 5,078,978 to Tarbet et al. discloses amino-pyridine-containing hydrocarbon ligands; U.S. Pat. No. 5,244,856 to Bruening et al. discloses polytetraalkylammonium and polytrialkylamine-containing hydrocarbon ligands; U.S. Pat. No. 5,173,470 to Bruening et al. discloses thiol and/or thioether-aralkyl nitrogen-containing hydrocarbon ligands; and U.S. Pat. No. 5,190,661 to Bruening et al. discloses sulfur-containing hydrocarbon ligands also containing electron withdrawing groups. These ligands are generally attached to the solid support via a suitable hydrocarbon spacer.
One problem with some of these compositions is that they are not as efficient as sometimes desired when using acid solutions because of the effect of acid on the ability of these compositions to complex transition and other metal ions as well as allowing for a greater variety of selectivity among the transition metal ions themselves.
The present invention ameliorates this problem.